*drained* event emitting on intermittent basis

[obihill]

Description

The drained event is emitting intermittently even when the queue is empty and idle.

Minimal, Working Test code to reproduce the issue.

# .env
DB_HOST="127.0.0.1"
DB_PORT=6379

// queue.js

import 'dotenv/config';
import { Queue } from 'bullmq';

const config = {connection: {
    host: process.env.DB_HOST,
    port: process.env.DB_PORT
}}; 
const queue = new Queue('Birds', config);

queue.add('pigeon', {color: ['brown', 'grey']});
queue.add('swift', {color: ['brown', 'black']});
queue.add('lark', {color: ['brown', 'black']});
queue.add('finch', {color: ['yellow', 'black', 'green']});

await queue.close();

// worker.js

import 'dotenv/config';
import { Worker } from 'bullmq';

const config = {connection: {
    host: process.env.DB_HOST,
    port: process.env.DB_PORT
}}; 
const worker = new Worker('Birds', async function(job){
    console.log('--WORKER--')
    console.log('job.id =', job.id);
    console.log('job.name =', job.name);
    console.log('job.data =', job.data);
    console.log('---');
}, config);

// monitor.js

import 'dotenv/config';
import { QueueEvents } from 'bullmq';

const config = {connection: {
    host: process.env.DB_HOST,
    port: process.env.DB_PORT
}}; 

const queueEvents = new QueueEvents('Birds', config);

queueEvents.on('completed', function(job){
    console.log('--ON-JOB-COMPLETED--')
    console.log('job.id =', job.id);
    console.log('job.name =', job.name);
    console.log('---');
});

queueEvents.on('drained', function(){
    console.log('--ON-QUEUE-COMPLETED--');
});

1. Open three terminal windows
2. Run node queue, node worker, and node monitor in corresponding windows
3. Notice on the third window [monitor] that the console.log message is emitted intermittently

I understand that the drained event is supposed to emit when there are no more tasks to process. Should this not happen once for each salvo of jobs i.e. after active jobs, and not repeatedly on an idle and empty queue?

Bull version

1.76.1

Additional information

[github-actions]

🎉 This issue has been resolved in version 1.76.3 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀